package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import org.springframework.data.redis.core.StringRedisTemplate;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;


    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key,Object value,Long time,TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time,TimeUnit unit) {
        String key=keyPrefix +id;
        //1.从redis查询店铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3.存在，直接返回
            return JSONUtil.toBean(json, type);
        }

        //判断命中的是否是空值
        if(json !=null){
            //返回一个错误消息
            return null;
        }

        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在,返回错误
        if(r == null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL,TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }

        //6.存在，写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(r),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback,Long time,TimeUnit unit){
        String key=CACHE_SHOP_KEY+id;
        //1.从redis查询店铺缓存
        String json= stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isBlank(json)){
            //3.存在，直接返回
            return null;
        }
        //4.命中，需要先把json反序列化对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r=JSONUtil.toBean((JSONObject)redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1.未过期，直接返回店铺信息
            return r;
        }
        //5.2.已过期，需要缓存重建
        //6.缓存重建
        //6.1.获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2.判断是否获取锁成功
        if(isLock){
            //6.3.成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                //重建缓存
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unlock(lockKey);
                }
            } );
        }

        //6.4.返回过期店铺信息

        return r;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
